The present invention relates to a radiation tomography apparatus and a radiation tomography method thereof.
An X-ray CT (Computed Tomography) apparatus that generates an image of a tomographic plane of a subject to be imaged using an X-ray corresponding to radiation has been known as a radiation tomography apparatus. The X-ray CT apparatus has been used in widespread applications such as medical and industrial applications with a human body and an object as subjects to be imaged.
The X-ray CT apparatus scans the periphery of a subject to be imaged with a subject's body axis direction as the axis and applies X-rays to the subject from a plurality of view directions through an X-ray tube. The X-rays radiated from the X-ray tube are blocked or cut off thereby forming an X-ray so as to be applied to an imaging area of the subject. The X-rays transmitted through the subject from the plural view directions via the collimator are detected by an X-ray detector array for each of the view directions, and a tomographic image corresponding to the imaging area of the subject is reconstructed and generated based on detection data generated by the X-rays detected by the X-ray detector array.
A region of a subject to be imaged and the purpose of imaging it have been diversified for the X-ray CT apparatus. There has thus been a demand for an improvement in the image quality such as resolution and speeding-up of its imaging. In order to meet such a demand, the X-ray CT apparatus has an X-ray detector array in which a plurality of X-ray detection elements are arranged in array form so as to be capable of obtaining a plurality of tomographic images while the periphery of the subject is being scanned with one rotation. The X-ray detector array has X-ray detection modules in which X-ray detection elements for detecting an X-ray are arranged plural in array form. In order to facilitate its manufacture, a plurality of X-ray detection modules are configured so as to be disposed adjacent to both a channel direction and a body axial direction.
Since the plurality of X-ray detection elements are disposed adjacent to one another in the X-ray detector array in which the plurality of X-ray detection elements are arranged in array form, crosstalk might occur among the X-ray detection elements due to a detected X-ray. Therefore, when a tomographic image is reconstructed and generated based on detection data containing the crosstalk, there might be cases where in the X-ray CT apparatus, a reduction in the contrast of a tomographic image and artifacts occurred and the quality of an image was deteriorated.
In order to prevent the deterioration of the image quality due to the crosstalk, various methods have heretofore been proposed. In the prior art, for example, the generated amounts of crosstalk are determined every X-ray detection elements in advance, and detection data are corrected using the determined generated amounts of crosstalk (refer to a patent document 1, for example).
[Patent Document 1]Specification of U.S. Pat No. 4,897,788
Since, however, the periphery of a phantom was scanned with the body axial direction as the axis in the prior art, it was easy to determine the generated amounts of crosstalk every X-ray detection elements in the channel direction. However, it was difficult to obtain the generated amounts of crosstalk in the body axial direction. Therefore, the prior art encountered difficulties in preventing deterioration of the quality of an image due to the crosstalk in the body axial direction. Since there are cut lines or breaks between the adjacent X-ray detection elements at the boundaries among the plurality of X-ray detection modules as viewed in the boy axial direction in particular, the X-ray detection elements lying in the neighborhood of the boundaries of the X-ray detection modules as viewed in the body axial direction and the X-ray detection elements lying therearound are different from one another in the number of the X-ray detection elements respectively adjacent thereto, and profiles of the generated amounts of crosstalk in the body axial direction become discontinuous. Therefore, a reduction in the contrast of a tomographic image and the occurrence of artifacts happened noticeably.
Since the generated amount of crosstalk obtained in advance is used without using the generated amount of crosstalk at the actual acquisition of detection data in the prior art, it was not possible to correct the image quality with higher accuracy and hence sufficiently improve the image quality.